Parboil the beef plate, bones, and tendon in the Instant Pot for 2 minutes. Wait 5 minutes, then release the pressure (waiting first prevents spilling and spraying).
Drain and wash all the meats.
Add the bones, beef plate, and tendon to the clean Instant Pot with pounded lemongrass, a whole onion, salt, rock sugar, MSG, and the bún bò Huế seasoning cubes. Add water.
Pressure cook on high for 15 minutes.
While it cooks, cook the pork blood separately.
Let the pressure release naturally.
Remove all the bones, lemongrass, and onion.
Season with more salt and chicken powder to taste.
Add in the cooked pork blood.
For the chili oil, fry the green onion whites in oil until golden. Turn off the heat and let cool. Stir in the bún bò Huế seasoning packet and add the oil to the broth.